Description

This project is a compact modular flight controller and groundstation / tracking station for model rocketry and other similar craft.

It uses an STM32F411CEU6 ARM Cortex M4 processor and has a mainboard which contains the MCU, flash memory and radio link (HopeRF RFM69HW) and battery management. There is a flight controller mezzanine card which contains many sensors, a GPS module, locating buzzer and four high power FETs for switching booster igniters on multistage rockets. The flight mezzanine also includes GPIO to connect servos for active stabilization in future.

There will also be a groundstation mezzanine board for use in car and on-foot tracking, which contains a bluetooth link for remote phone link and an OLED display for easy viewing of GPS coordinates without a phone or laptop. With all mezzanine cards the Li-po battery slots between it and the main board and is a click-fit into the JST connector.

Details

The software for the flight computer is configured using a Chrome app. This has the advantage of being truly cross-platform and even allows the device to be programmed using either Bluetooth or USB-OTG from a phone in the field. This can be handy when you are in the middle of nowhere and need to change a parameter in your configuration due to changing weather conditions! The software will come with a selection of 'apps' - preconfigured setups which can be selected fast, like a simple GPS logger, single-stage rocket, two-stage rocket, etc. In future users will be able to create their own apps and share them (as an XML or JSON file which can be opened and saved in the Chrome app). In addition to the app system, there is also a full editor which allows the user to completely configure all aspects of the flight computer. This includes a fully-featured event system that tracks the various stages of flight (both through time, sensors and uplink) and allows actions to be triggered.

In addition to the mezzanine cards mentioned in the description above, a future card will contain multiple radio modules for use as a tracking station. These are standalone radio relays which can be deployed down-range of a larger launch site and employ a mesh network to relay telemetry and tracking data to the launch site. If the GPS system fails on the rocket, then the signal strength readings from the relays may also be used to give a crude indication of where the rocket may have landed. In a flat environment like American deserts this may seem trivial, but in Scottish hills this could be a valuable feature.

Project Logs

The pressure is on for us to get a prototype ready for International Rocketry Week 2015 at Lapwing Lodge near Glasgow in Scotland! This event, only a week away, is a very popular week-long camp in a rural area at the top of Britain where amateurs can come from all over the world to launch their rockets. One of our project members, Phil, has been attending for years and wants to attempt a very high launch this year for which he wants the flight computer ready to record!

We have the boards back from the fab house (Elecrow) and Matt, the main hardware designer, is hastily assembling some for various members of the team to play with their parts so they can work on the embedded software. My part (Laurence) is the Chrome app and USB connection for programming. I am currently looking at USB-CDC and USB-Serial at the moment, although USB-HID is also possible if it works out easier. Making the system work on PC is one challenge, but getting it happy on Android is another! For IRW we would be happy with just PC comms, but it would be nice to demonstrate phone-only programming to the other fliers there.